A lottery security director who was convicted of fixing a $16.5m lottery jackpot also allegedly rigged several other lottery random-number generators to be able to predict the winning numbers, according to Iowa investigators.

The Obama campaign has attempted to play down the apparent excitement generated by Mitt Romney's new running mate Paul Ryan, a move that boosted crowds at the Republican presidential challenger's events.

A lottery security director who was convicted of fixing a $16.5m lottery jackpot also allegedly rigged several other lottery random-number generators to be able to predict the winning numbers, according to Iowa investigators.